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Objectives - Chapter 14 1. What is an exploitative interaction? 2. Define Functional response 3.Define Numerical response 4.Describing predator/prey interactions.

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Presentation on theme: "Objectives - Chapter 14 1. What is an exploitative interaction? 2. Define Functional response 3.Define Numerical response 4.Describing predator/prey interactions."— Presentation transcript:

1 Objectives - Chapter What is an exploitative interaction? 2. Define Functional response 3.Define Numerical response 4.Describing predator/prey interactions mathmatically (Lotka Volterra models)

2 Exploitation (Predation, etc.) Most important biological interactions - Consumption of one organism (or part thereof) by another

3 Exploitation (Predation, etc.) Predator and prey Kill and consume

4 Exploitation (Predation, etc.) Herbivore and plant Consume, but may not kill

5 Exploitation (Predation, etc.) Parasite and host Consume, but may not kill, reducing fitness

6 H. Bogert with Leeches Hirudinea

7 Leech

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9 Parasites Eat only one or two different organisms during a lifetime--- as opposed to other types of predators (e.g., grazers that eat a large number of plants) Host and habitat are the same!!! Leopold - “parasites kill far more organisms than we know” - selection pressure

10 Exploitation (Predation, etc.) Parasitoid and insect Consume and kill

11 Exploitation (Predation, etc.) Pathogen Disease, debilitating conditions of host

12 Exploitation Many relationships not clear cut E.g., Competition between two organisms where one eats the other.

13 Exploitation Many relationships not clear cut E.g., Herbivore killing plant it feeds on

14 Exploitation (Predation, etc.) Definitions of each are problematic---- Common to all interactions: One organism living at the expense of another.

15 Responses of Consumer Species to Variation In the Abundance of Their Food Species As the density of the food species increases, the consumer species responds by: 1.Increasing the rate at which they eat the food species. “Functional Response”

16 Theoretical Functional Response Curves In Type 1 exploitation interactions, time required to find prey (search time) is the only factor limiting consumption rate. Satiation Increasing abundance of food organism proportionally reduces searching time, increasing rate of prey consumption. Consumption rate increases until consumers cannot eat any faster (Satiation) Lo Prey Density Hi Consumption Rate

17 Theoretical Functional Response Curves In Type 2 exploitation interactions, consumption rate is influenced by two separate processes: Searching “Handling” Satiation At low prey density, searching time limits consumption rate. At moderate prey density, handling time limits consumption rate. Lo Prey Density Hi Lo Prey Density Hi Consumption Rate At high prey density, predator consumption rate limited by satiation.

18 Theoretical Functional Response Curves In Type 3 exploitation interactions, the consumer eats multiple food species. When a food species is rare, the consumer may ignore it and focus on consuming more common species. As a food species becomes more abundant, the consumer switches to eating more of that species. Prey Switching and Learning Curve Limit Prey Consumption Here

19 Responses of Consumer Species to Variation In the Abundance of Their Food Species As the density of the food species increases, the consumer species responds by: 2.Increasing population size due to increased survivorship and reproduction AND immigration from surrounding areas. “Numerical Response”

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21 Numerical Response: 1. Effect of prey on predator reproduction: Increased food (prey) Increased growth rate, survivorship Earlier reproduction, increased offspring/female, increased females Increased R and r, increased # predators Predator Responses

22 Numerical Response: 2. Effect of prey density on predator migration Predator Responses Increased food Increased # predators Predators attracted Residents remain

23 Brown Lemming1-5/acre Numerical Response-Field Examples

24 Brown Lemming Pomarine Jaegeruncommon breeding breeding no breeding 4/ m i 2 18/mi 2 Numerical Response-Field Examples

25 Brown Lemming Pomarine jaeger uncommon breeding breeding no breeding 4/ m i 2 18/mi 2 Short-eared OwlAbsentone recordbreeding 3-4/mi 2 Numerical Response-Field Examples

26 Brown Lemming Pomarine jaeger uncommon breeding breeding no breeding 4/ m i 2 18/mi 2 Short-eared OwlAbsentone recordbreeding 3-4/mi 2 Snowy OwlScarcebreedingbreeding no breeding.2-.5/mi /mi 2 many nonfew non Numerical Response-Field Examples

27 Responses of Consumer Species to Variation In the Abundance of Their Food Species As the density of the food species increases, the consumer species responds by: 3. Combination of #1 and #2. “Combined Response”

28 Mini Summary: To regulate the food species population, the consumer population must be able to eat food organisms faster than they can reproduce, as determined by: 1.Consumption rate: (Functional Response). 2.Consumer Species Rate of Increase: (Numerical Response) 3.Combined Response of Consumer Species 4.Consumer Efficiency: Number of food organisms required to produce a new consumer organism.

29 Prey Model - Figure dN h /dt = r h N h - pN h N p dN h /dt = Rate of prey population change r h = intrinsic growth rate of prey p= ingestion efficiency N h = density of prey N p = density of predators Lotka Volterra Predator-Prey Model

30 Predator Model – Fig dN p /dt = cpN h N p - d p N p dN p /dt = rate of predator change c= production efficiency of predator p= ingestion efficiency N h = density of prey d p = death rate of predator N p = density of predators Lotka Volterra Predator-Prey Model

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33 Prey population Predator population Predator increasing Predator decreasing

34 Lotka Volterra Predator-Prey Model Prey population Predator population Predator isocline Predator increasing Predator decreasing

35 Prey population Predator population Prey increasing Prey decreasing Lotka Volterra Predator-Prey Model

36 Prey population Predator population Prey isocline Prey increasing Prey decreasing

37 Prey population Predator population Prey increasing Prey decreasing Prey increasing Prey decreasing Predators increasing Predators decreasing Predators increasing Predators decreasing Lotka Volterra Predator-Prey Model

38 Prey population Predator population

39 Lotka Volterra Predator-Prey Model Prey population Predator population

40 Lotka Volterra Predator-Prey Model Prey population Predator population

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42 Question: 1. Are prey species populations being regulated by density dependent or density independent controls? 2. What about the predator species? Predator-Prey Model

43 Types of exploiters Functional response Numerical response predator reproduction predator migration Lotka Volterra predator-prey model Summary for Today

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